Modelling the quantitative effect of oxygen on the ageing of primed celery seeds

High seed quality is a prerequisite for profitable crop production, but quality declines by ageing during storage. Whereas effects of temperature and humidity are well known, there is limited knowledge on the effect of oxygen. Here, we report on the quantitative effect of oxygen on seed ageing. Primed seeds from celery (Apium graveolens) were used as a model, because of their relatively short shelf life. The seeds were stored for up to 7 years at combinations of four relative humidity levels (16, 33, 43 and 60% RH), four temperatures (5, 13, 20 and 30°C) and six oxygen levels (≈1, 5.2, 10, 21, 50 and 99% on volume basis). A strong effect of low oxygen levels was observed at all temperatures and the three lower humidity levels. Modelling the viability data revealed a linear double logarithmic relationship between the oxygen level and the storage time at which the seed lot viability declined to 50% (p₅₀). The models also showed that each halving of the oxygen level increased seed longevity by around 72%. This implies that reduction of the environmental oxygen level to a level below 1% increased the shelf life of the primed celery seeds by a factor of 11. For seeds pre-equilibrated at 60% RH, the effect of lowering the oxygen level below 21% was much less pronounced and even absent at 30°C. The large effect of low oxygen level during dry storage of seeds provides opportunities to prolong the shelf life of seeds. Options for practical application are discussed.